Rhythm disorders Flashcards
Checks to perform on an ECG
- Correct recording? (px name/age/EMIS)
- Review the signal quality and leads
- Verify the voltage and paper speed
- Review the patient background
What is the step by step process of interpreting an ECG?
Rate and Rhythm
P-wave and P-R interval
QRS duration
QRS axis (cardiac axis)
ST segment
QT interval/T wave
What are the features of a sinus rhythm ECG?
Each P wave is followed by a QRS complex (1:1) // Regular rate and normal bpm
What are the features of a sinus bradycardia ECG?
Each P wave is followed by a QRS complex (1:1)
Regular rate but SLOW bpm (<65)
What are the features of a sinus tachycardia ECG?
Each P wave is followed by a QRS complex (1:1)
Regular rate but FAST bpm (>100)
What are the features of a sinus arrhythmia ECG?
Each P wave is followed by a QRS complex (1:1)
Irregular rate (variable R-R intervals)
Normal range of bpm (65-100)
What does sinus mean?
Rhythm generated by the SAN
What can cause sinus bradycardia
Medication
Normal - red. HR for athletes due to muscular heart
Vagal stimulation
What can cause sinus tachycardia
physiological response to stimulus
When can rate be faster and slower in sinus arrhythmia?
Slower - long expiration
Faster - long inspiration
How to calculate Heart rate
300/no. large squares
What is happening in atrial fibrillation?
Abnormal irregular contraction of atria
What are the features of an atrial fibrillation ECG?
Oscillating baseline (atria contracts asynchronously), Irregular Rhythm,
Slow Rate
What is a complication of atrial fibrillation?
Clotting - due to turbulent flow
What is happening in atrial flutter?
Abnormally fast REGULAR contraction of atria
What are the features of an atrial flutter ECG?
Saw-tooth pattern in baseline (not present in everyone)
Multiple P waves followed by QRS complex (2:1 or 3:1)
What is happening in first degree heart block?
Delay in Atrioventricular Node in conducting QRS complex, typically with aging
What are the features of a first degree heart block ECG?
Prolonged PR segment/interval
Regular rhythm
What causes first degree heart block
Ageing
What are the two types of second degree heart block?
Mobitz Type I and Mobitz Type II
What is happening in second degree heart block?
Delay in Atrioventricular Node in conducting QRS complex, sometimes current does not reach the ventricles
What are the features of a Mobitz Type I Second Degree Heart Block ECG?
Gradual prolongation of PR segment/interval until there is a missing QRS.
Regularly irregular - (beat, beat, no beat) looped.
What is the cause of Mobitz 1 2º HB
diseased AVN
What are the features of a Mobitz Type II Second Degree Heart Block ECG?
No PR prolongation,
Regular P waves
Some missing QRS
Regular irregular (can follow 2:1 pattern or be completely random)
What can mobitz II 2º HB deteriorate into
3º HB
What are the features of a third degree heart block ECG?
P-P intervals are regular
R-R intervals are regular
But P and R intervals are completely irregular - non-sinus rhythm
What is happening in third degree heart block?
Complete block of AVN
However ventricular contraction still occurs (self stimulating), disjointed w/ atrial contrac
What is happening in ventricular tachycardia?
Ventricles are contracting too fast, disjointed atrial contraction, but regularly
What are the features of a ventricular tachycardia ECG?
Hidden P waves,
Regular and Fast Rate (100-200)
V.Tach risks
Cardiac arrest with deterioration in fibrillation
.: use defibrillator (shockable rhythm)
What is happening in ventricular fibrillation?
Cardiac Arrest - irregular extremely fast ventricular contractions (uncoordinated e- activity)
What are the features of a ventricular fibrillation ECG?
Irregular heart rate over 250bpm
How can you treat ventricular arrythmias?
Defibrillator - they are shockable rhythms
What is an example of a non-shockable rhythm?
Flat-lining - asystole
(adrenaline injections)
What causes movement of the ST segment
Perfusion defect
What is happening in ST-Elevation?
Perfusion defect caused by infarction
(tissue death due to hypoperfusion)
What are the features of an ST-Elevation ECG?
1:1 P waves and QRS complexes
Regular rate and normal BPM
ST segment is elevated by more than 2mm (2 tiny boxes) above isoelectric line
What is happening in ST-Depression?
Perfusion defec due to myocardial ischaemia
(coronary insufficiency/hypoxia)
What are the features of an ST-Depression ECG?
1:1 P waves and QRS complexes
Regular rate and normal BPM
ST segment is depressed more than 2mm (2 tiny boxes) below isoelectric line
Infarction vs Ischaemia
Infarction: Blood flow completely cut off -> necrosis
Ischaemia: Red. blood flow -> hypoxia
